New Tech Europe | Jan 2017 | Digital Edition

an absolute, single-turn encoder, ensures optimal torque utilization at any speed. Furthermore, closed- loop stepper motors are less noisy and vibrate less than open-loop stepper motors. Let’s consider the stepIM as our case. Lower energy consumption and keeping cool StepIM stepper motors are efficient consumers of energy. Unlike open- loop steppers that are always commanded with full current, resulting in heat and acoustic noise, current to the stepIM flows only when needed, for example, during acceleration and deceleration. Like servos, these steppers consume current proportionally to the actual torque required at any given moment. Since motor and integrated electronics run cooler, stepIM steppers can achieve the higher peak-torque levels associated with servos. Close match to performance requirements To make sure that there is enough torque to overcome disturbances and to avoid losing steps, open- loop steppers are routinely sized with at least 40% more torque than required by the application. Not so with closed-loop stepIM steppers. When these steppers are overloaded to a stall condition, they continue to hold against the load without losing torque. Upon removal of a blocking load, they continue to run. Maximum torque at any given speed is guaranteed while position sensors ensure that no steps are lost. Thus, closed-loop steppers can be sized to closely match the torque requirements of their application without the 40% extra margin.

Figure 4. A stepper’s torque decreases as its speed increases

Figure 5. Closed-loop technology advancements enable stepper motors to step into high-performance, high-speed applications formerly reserved for servos

Servotronix has embedded field- oriented, closed-loop control in its stepIM integrated, stepper motors. Figure 6. Servotronix’s stepIM with closed-loop control The integrated electronics control the stepper motor as a two-phase BLDC motor, implementing position loop, velocity loop, DQ control, as well as additional algorithms. Closed- loop commutation, by means of

Figure 6. Servotronix’s stepIM with closed-loop control

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